\documentclass{article}
\usepackage{multirow}
\usepackage{booktabs}
\begin{document}
\begin{table}[h!]
	\centering
	\caption{mycaption}
	\label{tab:test}
	\begin{tabular}{llll}
		\toprule
		\textbf{headerone} & \textbf{headertwo}     & \textbf{headerthree} & \textbf{headerfour}                           \\\midrule
		r1c1               & r1c2                   & r1c3                 & \multirow{4}{*}{norowlinesinthefirstfourrows} \\\cmidrule{1-3}
		r2c1               & r2c2                   & r2c3                 &                                               \\\cmidrule{1-3}
		r3c1               & r3c2                   & r3c3                 &                                               \\\cmidrule{1-3}
		r4c1               & r4c2                   & r4c3                 &                                               \\\midrule
		r5c1               & r5c2                   & r5c3                 &                                               \\\midrule
		r6c1               & r6c2                   & r6c3                 &                                               \\\midrule%another trailing comment
		r7c1               & r7c2                   & r7c3                 &                                               \\\bottomrule % trailing comment
		deliberately       & not got max ampersands                                                                        % trailing
	\end{tabular}
\end{table}
\end{document}
